1. Field of the Invention
The present invention pertains to method and apparatus for draining flat-roofed or low-slope roofed structures, and particularly to panels used for such purposes.
2. Related Art and Other Considerations
Since the beginning of "flat roof" building construction, it has been recognized that stagnant ponds of water are harmful. When water is left standing on any type of waterproof membrane,it accelerates the aging process of the membrane in that area. Accordingly, any place frequently covered by residual water left from a rain or snow melt will experience early failure.
Many schemes have been developed over the years to eliminate residual water ponds from what is now known as "low-slope roofing." For example, U.S. Pat. No. 4,014,145 to Groves teaches the art of using "roof saddles" to assist in eliminating standing water. As used herein, a roof saddle is a flat-bottomed pyramid which has an essentially elongated diamond-shaped bottom and a central peak or vertex on its top surface. Four surfaces of the saddle sloping down from the central vertex serve to allow water to run off the saddle for collection in drains provided in the roof. Drainage systems comprised of drain pipes and roof saddles have been the preferred method of eliminating residual water from essentially flat roofs for many years.
On very large roof expanses, building designers have often planned on the structural portion of the roof decks being built as a series of minor (low slope) pyramids to provide high centers and low valleys. A drain pipe was installed at each confluence of four valleys. Unfortunately, all too often the valley between two structural pyramids would become a pond for standing water. The typical solution usually is the utilization of roof saddles in the valleys to eliminate residual water.
Over the years, many methods have been employed to create and install roof saddles. Historically, the most frequently used method has been that of the roofing contractor forming saddles at the building site from low-cost fiber board or expanded polystyrene plastic foam. This on-site method is very slow and labor intensive.
As building construction contractors strive to finish their buildings faster in order to reduce costs, the "hand-made, on-the-job" method has become less favored. Rather, in order to reduce escalating labor costs, roofing contractors have increasingly turned to "pre-fabricated" saddles. Pre-fabricated saddles are custom made at a factory purportedly for speeding up the installation process.
Unfortunately, several problems arise utilizing the prefabricated method. For example, conventional "factory-made" roof saddles also turn out to be labor-intensive processes. Moreover, although factory labor tends to be lower in cost than construction labor, pre-fabricated roof saddle systems are also relatively expensive. In addition there is the problem of factory lead time. That is, a long lead time for factory orders (e.g., eight weeks) is inconsistent with the fast-track building approach employed by many building system managers. These managers desire to order and receive their material in just a few weeks. Therefore, transferring a labor-intensive process from the construction site to the factory does little to help the problem.
Ostensibly to reduce the labor costs inherent with pre-fabricated roof saddle systems, a method and apparatus for fabricating roofing saddles by computer-controlled machinery is taught in U.S. Pat. No. 5,663,882 to Douglas. While such computerized systems do reduce the cost of manufacturing pre-formed saddles, other problems are not addressed and some problems are spawned.
In computerized systems, the saddle components are built precisely to the length and width dimensions given in the architects' drawings. However, at the construction site, it is often necessary to make expedient changes. For example, for various reasons the roof configuration at the building site may not turn out to be strictly in accordance with the architectural drawings. For example, it frequently turns out that the drainage pipes have been moved in order to accommodate changes of the more important structural components of the building. In fact, in some cases the drainage pipes must be moved several feet in order to accommodate other newly added, or changed, building components. In such cases, the precisely manufactured conventional saddle diamonds are either too short or too long and thus will not form the drainage low-point at the drain pipe. Rather, a pre-fabricated saddle installed in an altered structure could either cover the drain pipe, or could instead form a low point several feet short of the drain. In either case, the precisely made conventional saddle is useless until extensive field cutting and repairs are made. Any cost or time saving otherwise attributable to a pre-fabricated conventional saddle is more than offset by having to modify such a precut saddle system when the saddle was made to architectural dimensions rather than actual building measurements.
Another problem with conventional pre-fabricated roofing saddles is the complexity (and thus cost) of the equipment required for computer controlled cutting and labeling. For conventional pre-fabricated saddles, an infinite variety of angles may be required. The requirement for widely varying angles contributes to the complexity of the saddle-fabricating machinery, and also to the frequency of repairs of such machinery.
Furthermore, saddles produced by conventional pre-fabricated saddle production systems have proved difficult to install, even when the actual structure matches the design drawings. In industry practice, the materials are shipped in a stretch-wrapped bundle approximating a four-foot cube. This package is comprised of many small pieces, as well as odd-shaped medium sized and large pieces. The smaller pieces are fragile and thus susceptible to being easily damaged. Also, as mentioned above, an infinite variety of angles are cut to accommodate any given roof shape. A system of labeling is required so that the installer can determine not only which pieces abut each other, but which edges of each piece must be joined. Many hours can be exhausted searching for the correct pieces to join, then matching the proper edges. If two packages are opened at the same time, the pieces can become intermixed, thus increasing the time spent to sort things out. If a breeze starts up, which is often the case on a rooftop, the smaller pieces can become lost. Thus, working with conventional pre-fabricated saddles transported in the plastic-wrapped cubes somewhat resembles solving an expensive jigsaw puzzle. Even with a complex labeling system, finding the correct pieces to join can become a challenge.
What is needed therefore, and an object of the present invention, is a roofing drainage panel unit which is inexpensive yet easy to fabricate, transport, and install.